Book/Dissertation / PhD Thesis

FZJ-2022-01997

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Topological magnonic properties of two-dimensional magnetic materials

Zhang, L. (Corresponding author)FZJ*

2022
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-621-2

Please use a persistent id in citations: http://hdl.handle.net/2128/31143

Abstract: Spintronics is based on the transport of information by the spin of electronsrather than charge current so as to avoid the Joule heat. Among it,magnons, as the most elementary excitations in magnetic materials, haveemerged as a prominent tool in electrical and thermal manipulation andtransport of spin. Importantly, magnonics as a field is considered as one ofthe pillars of modern spintronics.In this thesis, the linear spin-wave theory is utilized to explore the magnonicproperties based on the effective spin Hamiltonian, parameterizedfrom the first-principles calculations and fitting to experiments. Inspired bythe experimental result, a family of two-dimensional metal-organic frameworkswith the Shastry-Sutherland lattice are calculated from first-principles,and corresponding applications in spintronics and magnonics are investigatedin the thesis. Additionally, combined with inelastic neutron scatteringresults, the magnonic topological properties are systematically exploredin the multiferroic ferrimagnet Cu2OSeO3. The experimental magnon dispersionsare well fitted, when considering the Heisenberg-Dzyaloshinsky-Moriya interaction model, and the Weyl points are forecasted whose positioncan be controlled by changing the Dzyaloshinsky-Moriya interaction ofthe material. Moreover, a measurable thermal Hall conductivity is predicted,which can be associated with the emergence of the Weyl points.Notably, in realistic two-dimensional materials, e.g., ferromagnetic honeycombmaterials, the Dzyloshinskii-Moriya interaction is often accompaniedby the Kitaev interaction, which poses a challenge to distinguish theirmagnitude. In the thesis, we demonstrate that it can be done by accessingmagnonic transport properties and rotating the magnetization in the system.By studying honeycomb ferromagnets that exhibit at the same time theDzyaloshinskii-Moriya interaction and Kitaev interaction, complex magnonictopological properties are revealed accompanied by intricate magnonic transportcharacteristics represented by thermal Hall and magnon Nernst effects.Moreover, the effect of a in-plane magnetic field is investigated, showingthat it can break the symmetry of the system and bring drastic modificationsto magnonic topological transport properties, serving as hallmarks of therelative strength for anisotropic exchange interactions. Furthermore, basedon our proposed strategy, the spin interactions in CrSiTe3 and CrGeTe3 arepredicted and their potential applications in topological magnonics are explored.

Note: Dissertation, RWTH Aachen University, 2022

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Contributing Institute(s):

1. Quanten-Theorie der Materialien (PGI-1)
2. Quanten-Theorie der Materialien (IAS-1)
3. JARA-FIT (JARA-FIT)
4. JARA - HPC (JARA-HPC)

Research Program(s):

1. 5211 - Topological Matter (POF4-521) (POF4-521)

Appears in the scientific report 2022

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